﻿/*
* Lazy Load - jQuery plugin for lazy loading images
*
* Copyright (c) 2007-2009 Mika Tuupola
*
* Licensed under the MIT license:
*   http://www.opensource.org/licenses/mit-license.php
*
* Project home:
*   http://www.appelsiini.net/projects/lazyload
*
* Version:  1.5.0
*
*/
(function ($) {
  $.fn.lazyload = function (options) {
    var settings = {
      threshold: 0,
      failurelimit: 0,
      event: "scroll",
      effect: "show",
      container: window
    };
    if (options) {
      $.extend(settings, options);
    }
    /* Fire one scroll event per scroll. Not one scroll event per image. */
    var elements = this;
    if ("scroll" == settings.event) {
      $(settings.container).bind("scroll", function (event) {
        var counter = 0;
        elements.each(function () {
          if ($.abovethetop(this, settings) ||
$.leftofbegin(this, settings)) {
            /* Nothing. */
          } else if (!$.belowthefold(this, settings) &&
!$.rightoffold(this, settings)) {
            $(this).trigger("appear");
          } else {
            if (counter++ > settings.failurelimit) {
              return false;
            }
          }
        });
        /* Remove image from array so it is not looped next time. */
        var temp = $.grep(elements, function (element) {
          return !element.loaded;
        });
        elements = $(temp);
      });
    }
    this.each(function () {
      var self = this;
      //我就把这里的一段代码删除了
      /* When appear is triggered load original image. */
      $(self).one("appear", function () {
        if (!this.loaded) {
          $("<img />")
.bind("load", function () {
  $(self)
.hide()
.attr("src", $(self).attr("_src"))
[settings.effect](settings.effectspeed);
  self.loaded = true;
})
.attr("src", $(self).attr("_src"));
        };
      });
      /* When wanted event is triggered load original image */
      /* by triggering appear.                              */
      if ("scroll" != settings.event) {
        $(self).bind(settings.event, function (event) {
          if (!self.loaded) {
            $(self).trigger("appear");
          }
        });
      }
    });
    /* Force initial check if images should appear. */
    $(settings.container).trigger(settings.event);
    return this;
  };
  /* Convenience methods in jQuery namespace.           */
  /* Use as  $.belowthefold(element, {threshold : 100, container : window}) */
  $.belowthefold = function (element, settings) {
    if (settings.container === undefined || settings.container === window) {
      var fold = $(window).height() + $(window).scrollTop();
    } else {
      var fold = $(settings.container).offset().top + $(settings.container).height();
    }
    return fold <= $(element).offset().top - settings.threshold;
  };
  $.rightoffold = function (element, settings) {
    if (settings.container === undefined || settings.container === window) {
      var fold = $(window).width() + $(window).scrollLeft();
    } else {
      var fold = $(settings.container).offset().left + $(settings.container).width();
    }
    return fold <= $(element).offset().left - settings.threshold;
  };
  $.abovethetop = function (element, settings) {
    if (settings.container === undefined || settings.container === window) {
      var fold = $(window).scrollTop();
    } else {
      var fold = $(settings.container).offset().top;
    }
    return fold >= $(element).offset().top + settings.threshold + $(element).height();
  };
  $.leftofbegin = function (element, settings) {
    if (settings.container === undefined || settings.container === window) {
      var fold = $(window).scrollLeft();
    } else {
      var fold = $(settings.container).offset().left;
    }
    return fold >= $(element).offset().left + settings.threshold + $(element).width();
  };
  /* Custom selectors for your convenience.   */
  /* Use as $("img:below-the-fold").something() */
  $.extend($.expr[':'], {
    "below-the-fold": "$.belowthefold(a, {threshold : 0, container: window})",
    "above-the-fold": "!$.belowthefold(a, {threshold : 0, container: window})",
    "right-of-fold": "$.rightoffold(a, {threshold : 0, container: window})",
    "left-of-fold": "!$.rightoffold(a, {threshold : 0, container: window})"
  });
})(jQuery);
